"The Opening Post, is regarding regular expressions for many aspects where its not needed?"

If you have a drivers license, that's great up until your car breaks down. At that point you're left on the side of the road, maybe you have a toolkit, but what are you going to do with it when you don't know how to work a ratchet?

Not only is it beneficial to understand how these functions are working underneath the surface (afaik, filter_var is just a wrapper for nearly the same regular expressions), but it's good practice for building regular expressions you may need down the road. Same thing if you need a variation on a theme; what happens if you're looking for a specific type of email address?

Good information to add though, filter_var() can be a handy tool to know in addition to regular expressions!